1. Technical Field
The present invention relates to mobile networks including different IP Multimedia Subsystem (IMS) entities, and more particularly, relates to solutions for providing simplification of required policy control operations and compatibility between IMS entities based on different release specifications within mobile networks.
2. Related Art
Modern mobile networks such as those networks standardized by 3GPP (3rd Generation Partnership Project) specifications including all GSM (Global System for Mobile Communications) and 3rd generations of GSM networks, are seamless integration of digital cellular networks and personal communications systems to provide telecommunication services including, for example, mobile data network services and IP multimedia services.
Each 3GPP system may include a core network and a radio access network infrastructure using General Packet Radio Service (GPRS) and Enhanced Data Rates for Global Evolution (EDGE) technologies or supporting Universal Terrestrial Radio Access (UTRA) operable in both Frequency Division Duplex (FDD) and Time Division Duplex (TDD). The core network (CN) may be logically divided into circuit switched (CS) and packet switched (PS) domains with CN entities provided for user traffic and related signaling, and an IP Multimedia Subsystem (IMS) with CN entities provided for IP multimedia services. Some CN entities such as Home Subscriber Server (HSS), Home Location Register (HLR), Authentication Center (AuC), Visitor Location Register (VLR), and Equipment Identify Register (EIR) may be common to the PS and CS domains, while other CN entities such as Mobile Switching Center (MSC) and Gateway MSC are specific to the CS domain to handle circuit switched services to/from mobile stations, and Gateway GPRS (general packet radio service) Support Node (GGSN) and Serving GSN (SGSN) are specific to the PS domain to handle the packet transmission to/from the mobile stations.
For IP multimedia services, functional IMS entities, such as Call Session Control Function (CSCF), are provided to handle CSCF related procedures, including establishing PDP (Packet Data Protocol, e.g., IP) context for IMS related signaling, registration and other procedures for IMS sessions. CSCF can act as Proxy CSCF (P-CSCF) to serve as a first contact point for a user equipment (UE) (i.e., device allowing a user to access to network services, such as, a mobile station) within the IP multimedia subsystem (IMS), Serving CSCF (S-CSCF) to handle session states in the network, or an Interrogating CSCF (I-CSCF) to serve as a contact point within an operator's network for all IMS connections destined to either a subscriber of that network operator or a roaming subscriber in a given service area. See, 3GPP Technical Specification (TS) 23.002, V5.9.0 (December 2002) “Network Architecture”; 3GPP TS 23.101, V4.0.0 (April 2002) “General UMTS Architecture”; and 3GPP TS 23.110, V4.0.0 (April 2001) “UMTS Access Stratum: Services and Functions”; and 3GPP Technical Specification (TS) 23.228, V6.0.1 (January 2003) “IP Multimedia Subsystem (IMS)”. All 3GPP (GSM/3G) specifications can be found and downloaded from the 3GPP server under ftp://ftp.3gpp.org/specs, and are hereby incorporated by reference herein. In addition, mechanisms for creating, maintaining and updating 3GPP specifications (including different Releases of a given 3GPP specification with new or changed functionality) can also be found in 3GPP Technical Specification (TS) 21.900 V5.0.1 (September 2002) “Technical Specification Group Working Methods.”
However, challenges remain when providing equipment interoperability and compatibility between various functional entities in a given 3GPP specification, each time new functionality or new feature is introduced and/or existing functionality is modified and, hence, a new Release of a given specification is introduced.
For example, a Policy Decision Function (PDF) has been standardized as part of the Proxy CSFC (P-CSFC) to supervise an IMS session, make policy decisions based on the IMS session and media related information, and then exchange decision information with the GGSN via a Go interface, as set forth in the 3GPP TS 29.207 V.5.2.0 (December 2002) “Policy Control over Go Interface”, Release 5. The PDF is used to generate a set of binding information to bind the IMS level and the GPRS bearer level of an IMS session, and send the binding information to the GGSN, via the user equipment (UE). The GGSN then searches PDF address from the set of binding information received from the UE, identifies the correct PDF and verifies that the PDP context operations requested by the UE comply with the preceding negotiation on the IMS level; see also, and 3GPP TS 23.207 V.5.6.0 (December 2002) “End-To-End Quality of Service (QoS) Concept and Architecture”, Release 5; and 3GPP TS 29.208 V.5.2.0 (December 2002) “End-To-End Quality of Service (QoS) signaling flows”, Release 5.
According to the 3GPP Specification, Release 5 (December 2002), PDF is integrated into P-CSCF and only one IMS session is allowed for each PDF context. However, the 3GPP Specification, Release 6 (January 2003) is currently being planned so that PDF can be implemented in a separate network element that is separate from the P-CSCF. In addition, there may be several PDFs arranged in the core network (CN). As a result, even if P-CSCF is known, PDF may not be assumed by the core network (CN). A single P-CSCF may be configured to use the services of several PDFs, since several PDFs may exist in the core network (CN). Moreover, several IMS sessions are allowed for a single PDP (Packet Data Protocol, e.g., IP) context as currently being planned in the 3GPP Specification, Release 6 (January 2003). As a result, the UE may send/receive several session setup or modification requests (SIP INVITE) and can set up (or modify) one PDP context for several IMS sessions. If there are more than one PDFs in the core network (CN), the P-CSCF may send the authorization requests of different sessions to different PDFs.
However, if the GGSN is based on the 3GPP Specification, Release 5, the GGSN will only search one PDF address from the sets of binding information received from the UE, and send all sets of binding information to the same PDF. Some sets of binding information may be sent to wrong PDFs, which leads to reject decisions. Moreover, even if only a single-session per PDP (Packet Data Protocol, e.g., IP) context is used, a PDP context modification may be directed by the P-CSCF to a different PDF than that used at the activation of the PDP (Packet Data Protocol, e.g., IP) context. As a result, the GGSN may reject the PDP context modification request when noticing that the PDF address in the request received from the UE differs from the PDF address in the stored set of binding information. Furthermore, when several IMS sessions use the same PDP (Packet Data Protocol, e.g., IP) context, the GGSN cannot handle a modification request for some but not all IMS sessions within a single PDP (Packet Data Protocol, e.g., IP) context.
In general, if one or more functional entities such as the UE and PDF are based on the 3GPP Specification, Release 6, and another set of functional entities such as the GGSN, are based on the 3GPP Specification, Release 5, network equipments may not operate successfully. There is no way to ensure backward compatibility, when multiple IMS sessions are executed over one PDP (Packet Data Protocol, e.g., IP) context and there are functional entities in the network that are based on both the 3GPP Specification, Release 5, and the 3GPP Specification, Release 6.
Moreover, even if the functional entities are based on the same specification release, complicated operations are required at the GGSN and at the PDF to control the PDP context modifications initiated by multiple sessions and to manage the interoperation between the common PDP context and the different sessions policy controlled by separate PDFs.
Accordingly, there is a need for providing compatibility between IMS functional entities based on different Specification Releases. In addition, there is also a need for providing simplification of GGSN and PDF operations.